1. Field of the Invention
The present invention relates to an anti-after burn system for an internal combustion engine and, more particularly, to a system operative to supply additional air into an intake system of an internal combustion engine when the engine intake vacuum exceeds a predetermined vacuum level to prevent an after burn which would otherwise occur due to an excessively rich air-fuel mixture fed into the engine.
2. Description of the Prior Art
A prior art system of the class specified above has an anti-after burn valve which is opened and closed in response to variation in the engine intake vacuum. The valve open period is dependent on the magnitude of the variation in the engine intake vacuum. When the engine is started, the vacuum level in the intake manifold of the engine is widely varied from a level substantially equal to the atmospheric pressure to a high vacuum level, so that the anti-after burn valve is opened for a long period of time during which the additional air is fed into the intake manifold of the engine, resulting in the occurence of an engine stall or poor engine starting capability.